1. Field of the Invention
The present invention relates to a heat treatment apparatus using a rapid thermal annealing (hereinafter referred to as RTA) method, and to a method of manufacturing a semiconductor device using the heat treatment apparatus. In particular, the present invention relates to a heat treatment apparatus that is used in an annealing process conducted for activation after ion injection.
2. Description of the Related Art
In a manufacturing process of a semiconductor integrated circuit, heat treatment is an essential process for the activation of an impurity after ion injection and for the formation of a contact of an electrode. The RTA method is known as a heat treatment technique that is conducted by instantaneously applying heat for several to several tens of seconds. The RTA method is one in which a substrate is rapidly heated mainly using a halogen lamp or the like, and has a characteristic that it is possible to raise or lower a temperature for a very short time in comparison with the case of using an annealing furnace.
As miniaturization of an integrated circuit progresses, the formation of a layer with a relatively low heat-resistant temperature is increasing. For example, a gate of a transistor is metalized. The activation of the impurity after ion injection in a semiconductor is performed after the formation of the gate, and thus, a heating process for activation is desirably conducted at a low temperature and for a short time. Further, there is a request for formation of a shallow junction with miniaturization. In this case as well, it is considered that the RTA method is suitable for conducting the heating process for a short time while suppressing diffusion of the impurity.
A conventional RTA apparatus has a structure in which a semiconductor substrate is placed in a chamber made of quartz and heated by using the RTA apparatus as a heating means. A light source such as a halogen lamp is used as the heating means, and the semiconductor substrate is heated by radiation from the light source. The heating temperature is possible to reach approximately 1100° C., and can be raised for several to several tens of seconds. A nitrogen gas is flown through the chamber formed of quartz.
In the RTA method, the heating process is conducted with a steep temperature change for a very short time of several to several tens of seconds, and thus, the diffusion of the impurity due to heat can be suppressed. However, to the contrary, a temperature profile for rise and lowering of temperature is important, and a small difference of temperature susceptibly influences an annealing characteristic. Thus, the heating process with reproducibility has been difficult to be conducted.
It is considered that a holding time in a maximum temperature region is made long in order to enhance reproducibility. However, since the gate formed of a metal with low heat-resistance is deteriorated, such a step is impossible. Further, the ratio of absorption of radiation from the light source differs between a portion where a metal wiring is formed and a portion where a metal wiring is not formed in the semiconductor substrate. Thus, there has been a problem in that the substrate is distorted and cracked due to thermal stress and other problems.